The invention relates generally to microwave heating and, more particularly, to heating a material flowing through a waveguide applicator.
Cylindrical waveguide applicators, such as the applicator in the Model CHS microwave heating system manufactured and sold by Industrial Microwave Systems, L.L.C. of Morrisville, N.C., U.S.A., are used to heat material flowing through the applicator in a flow tube. The tube is positioned in a focal region of the cylindrical applicator to subject the flowing material to a concentrated, but uniform heating pattern. The geometry of the applicator and the dielectric properties of the material to be heated largely determine the position and radial extent of the focal region. For many applications, a tightly focused focal region works best. But that requires a small-diameter flow tube precisely positioned in the cylindrical applicator's narrow focal region for efficient, uniform heating. And changing the position of the focal region and its concentration is difficult. Consequently, uniformly heating material flowing in a larger flow tube and adjusting the focus of the microwave energy is difficult without changing the geometry of the cylindrical applicator.
Thus, there is a need for a microwave applicator that overcomes some of these shortcomings.